Non-Newtonian Power-Law Flows around Circular Cylinder under Aiding/Opposing Thermal Buoyancy

Abstract

This paper presents a comprehensive computational work on hydrodynamic and thermal phenomena of upward flow separation around a confined circular cylinder by aiding/opposing thermal buoyancy. For that purpose, let us consider a confined flow of Non-Newtonian power-law fluid around a heated/cooled circular cylinder in a two-dimensional vertical channel. The effects of thermal buoyancy and power-Law index on the flow separation and the average Nusselt number are studied for the conditions: (10 ≤ Re ≤ 40), (0.4≤ n ≤ 1.2), (-0.5 ≤ Ri ≤ 0.8), Pr = 50 and blockage ratio β = 0.2. In the steady flow regime the results show that the augmentation of the power-law index in the absence of thermal buoyancy causes a separation to grow. The adding buoyancy effect delays the separation in different power-law indices gradually and at some critical value of the buoyancy parameter it completely disappears resulting a stuck flow around a cylinder, whereas the opposing buoyancy effect causes an earlier wake behind cylinder. Moreover, the recirculation length is calculated to support the above finding. The decrease in the power-Law index increases the heat transfer rate. The Nusselt numbers are computed to predict the heat transfer rates of power-law fluids under the aiding/opposing thermal buoyancy condition.